1. Field of the Invention
This document relates to a solar cell, and more particularly, to dyes for a dye-sensitized solar cell.
2. Discussion of the Related Art
Nowadays, in order to solve a facing energy problem, various researches for energy that can replace existing fossil fuels have been advanced. Particularly, various researches for using nature energy such as a wind force, atomic energy, and solar energy for replacing petroleum resources to be exhausted within several decades have been advanced.
Because a solar cell uses solar energy, which is an infinite and environmental-friendly energy source, unlike other energy sources, the solar cell has been in the spotlight due to an energy shortage problem since a Si solar cell was developed in 1983.
However, due to a supply and demand problem of a Si raw material, such a silicon solar cell causes a keen competition between countries and has a high production cost. Many foreign and domestic research institutions suggest solving means for solving the problems, but it is still difficult to solve the problems. An alternative for solving such a serious energy problem is a dye-sensitized type solar cell, and the dye-sensitized type solar cell was developed by Dr. Micheal Graetzel's research team of Switzerland National ‘Ecole Polytechnique Federale de Lausanne’ (EPFL) in 1991 and has been in the spotlight in the academic world and has been researched by many research institutions.
Unlike a silicon solar cell, the dye-sensitized solar cell is a photoelectric chemical solar cell using photosensitive dye molecules for generating electron-hole pairs by absorbing visible rays and using a transition metal oxide for transferring generated electrons as a main constituent material. A typical dye-sensitized solar cell among conventional dye-sensitized solar cells is a dye-sensitized solar cell using a nano particle titanium oxide.
The dye-sensitized solar cell can be applied to an outer wall glass window of a building or a glass green house due to a cheap production cost and a transparent electrode, compared with an existing silicon solar cell, but due to low photoelectric conversion efficiency, a more research is necessary.
Because photoelectric conversion efficiency of a solar cell is proportional to the quantity of electrons generated due to absorption of sun light, in order to increase photoelectric conversion efficiency, by increasing a dye amount to be adsorbed to nano particles of a titanium oxide, a generation amount of electrons is increased, absorption of sun light is increased, and the generated excited electron should be prevented from being disappeared by an electron-hole recombination.
In order to increase a dye adsorption amount per unit area, an oxide semiconductor particle should be produced to a size of a nanometer level, and in order to increase absorption of sun light, a method of increasing a reflectivity of a platinum electrode or of mixing semiconductor oxide light scattering particles having a size of several micrometers to the dyes was developed.
However, because a conventional method has a limitation in improving photoelectric conversion efficiency of a solar cell, new technical development for improving photoelectric conversion efficiency is urgently requested.